This invention relates to the field of over-current protection devices, and particularly the field of resettable fuses. More specifically, the invention relates to resettable fuse devices that are fabricated from a conductive polymer material with a positive temperature coefficient (PTC). In a specific embodiment, the present invention relates to a junction box, for a cable harness or the like, that incorporates an array of conductive polymer PTC devices for over-current protection.
The use of conductive polymer PTC devices for over-current protection and for other applications has become well-known in the art. See, for example, U.S. Pat. No. 5,802,709 and the references cited therein. A particular form of conductive polymer PTC device that has achieved widespread use is the type fabricated from a layer of conductive polymer PTC material laminated between a pair of metal foil layers that are formed into electrodes. Devices of this type, and a method of fabricating them, are disclosed in U.S. Pat. No. 5,802,709, the disclosure of which is expressly incorporated herein by reference.
The use of resettable over-current protection devices is desired in certain applications, for example, cable harness junction boxes for motor vehicles. Where over-current protection is provided by standard fuses, the cable harness must be routed so that the junction box is accessible to replace blown fuses. Resettable over-current protection devices, by contrast, do not need to be accessible; hence, the location of the junction box is less important, and the cable harness can be routed more efficiently. Consequently, PTC over-current protection devices, especially devices made of a conductive polymer PTC material, have become more common in cable harness junction boxes.
Heretofore, those cable harness junction boxes that employ PTC conductive polymer devices for over-current protection have used a plurality of discrete devices. While such junction boxes have, for the most part, achieved satisfactory performance objectives, there has been a continuing need to reduce manufacturing costs below the costs associated with discrete devices.